1. Field of the Invention:
The present invention relates generally to improved systems for mounting batteries on spacecraft to assure their integrity, operability, and long life. Throughout this disclosure, the term "spacecraft" will be used in the generic sense to refer to spacecraft of all types whether they be launch vehicles, space stations, satellites, space probes, or other vehicles operable in a space environment.
2. Description of the Prior Art:
Nickel hydrogen batteries for spacecraft are typically mounted into the structure of the spacecraft by means of a plurality of cylindrical metallic sleeves which supportively receive individual cells. The functions of the sleeves are to (a) physically connect each cell to the battery structure and (b) conduct waste heat due to the operation of the cell to the base plate of the battery and thence to the spacecraft heat rejection system (e.g., an optical space radiator).
Numerous metals have been proposed for the fabrication of the battery cell sleeves. These have included aluminum, beryllium, magnesium and alloys of these metals. In actual fact, aluminum is the metal most commonly employed for this purpose. All of these materials meet the technical requirements of having high thermal conductivity, adequate ultimate strength, generally good fracture resistance, and low density. As is common in all space-related activities, weight is a serious consideration in the design and construction of battery cell sleeves such that materials other than metals are continuously being sought which possess all the characteristics noted above while being significantly lighter in weight.
In recent years, composite materials have more and more become materials of choice to replace metals in applications requiring strength and light weight. Composite materials, or "composites", incorporate clusters of elongated fibers of strong materials embedded in a slurry-like amorphous matrix which subsequently solidifies and binds the fibers together into a strong unit.
Graphite is a material which has outstanding thermal conductivity, especially in the pyrrolic form, and low density (.about.2 g/cm2). Pure graphite, however, is extremely brittle and for this reason, its use as a sleeve material has not previously been seriously considered. An additional non-technical but significant economic impediment to the use of graphite is that it can only be fabricated into formed parts from solid monoblocks by expensive machining.